Fruit infusion using a syrup which has been subjected to enzyme treatment and concentrated

ABSTRACT

A process is described for rapidly infusing fruit with sugar solutes by means of an infusion bath which is maintained at a substantially constant solutes concentration and viscosity during the course of the infusion process by removing infusion solution; exposing the solution to an enzyme; concentrating the solution; and returning the concentrated solution to the original infusion bath.

This is a division of application Ser. No. 466,411 filed Feb. 15, 1983,now U.S. Pat. No. 4,551,348.

FIELD OF THE INVENTION

This invention relates to the infusion of liquid-containing cellularproducts such as fruits or vegetables capable of undergoing osmoticexchange with a sugar solution.

BACKGROUND OF THE INVENTION

The preparation of infused fruit products has conventionally beencarried out by adding fresh fruit to a tank containing a warmconcentrated sugar solution or sugar syrup, and then stirring the fruitand sugar syrup together. Due to the greater amount of dissolved solidsin the bath versus that present in the fruit, osmotic exchange takesplace resulting in the infusion of sugar solids into the cellularportions of the fruit. During osmosis, the syrup diffuses inwardly intothe fruit while water contained within the fruit undergoing infusiondiffuses outwardly through the cell walls of the fruit.

A principal disadvantage associated with conventional fruit infusionprocesses is that the high bath concentrations necessary to infuse thefruit to the desired solutes level often cause the fruit to shrivel.

Although the rate of infusion of bath solutes into the fruitapproximates the rate of water loss, or exfusion, from the fruit earlyin the infusion process, at later times the loss of water from the fruitcontinues at close to its initial rate while the influx of solutes intothe fruit proceeds much more slowly. This loss of water from the fruitbecomes more pronounced as the bath solutes concentration is increased,and is responsible for the undesirable shrinkage observed when highlyconcentrated infusion baths are employed.

Shrinkage could theoretically be reduced by use of a lower-concentrationinfusion bath, but infusion rates decrease with decreasing bathconcentration. Also, the achievement of the desired solutes level in thefruit is further impeded by the concomitant dilution of the infusionbath by the fruit water, which unacceptably slows the infusion rate.

Shrinkage can be reduced by the use of a series of baths of graduallyincreasing concentration, but this approach is also slow and may presentmechanical difficulties. However, due to the necessity to avoid osmoticshock, typical fruit infusion processes employ infusion times of 10 daysto 2 weeks.

It is, therefore, an object of the present invention to provide aprocess for fruit infusion which allows a balance to be maintainedbetween fruit water loss (dehydration) and bath solutes infusion so thatthe fruit solutes may be raised to the desired level before detrimentalshrinkage due to dehydration occurs.

It is another object of the present invention to economically decreasethe time required to achieve the desired dehydration infusion of fruit.

It is another object of the present invention to provide a process forfruit infusion wherein the fruit is infused to about the 32 to 58%solids level, and a water activity level of about 0.96 to 0.82,preferably 0.96-0.85.

SUMMARY OF THE INVENTION

The above objectives of the present invention are achieved by a processwhich permits the rapid infusion of fruit to the desired solutes levelby means of an infusion bath which is maintained at a substantiallyconstant solutes concentration and viscosity during the course of theinfusion process. Such baths counteract the tendency of the infusionrate to decrease greatly due to the dilution of the bath by fruit waterand thus avoid the need for the use of highly-concentrated infusionbaths or a series of baths of increasing concentration. The process ofthe present invention also includes means for counteracting theundesirable thickening of the infusion bath due to exfusing fruitpectins.

DETAILED DESCRIPTION OF THE INVENTION

The fruits which may be infused in accordance with this inventioninclude apples, cherries, strawberries, peaches, dates, pineapple,papaya, banana, nectarines, blueberries, raspberries, mango,elderberries, loganberries, raisins, mellons, kiwi (sapota), soursop,grapes, plums and the like. Any fruit which is capable of undergoing anosmotic exchange with a sugar solution without substantial collapse ordamage to the internal cellular structure of the fruit product may beemployed. Almost all fruits possess this property; however, it has beennoted that the internal cellular structure of the Driscoll variety ofstrawberry collapses as a result of treatment with a fructose containingsugar solution. Thus, this strawberry type is incapable of undergoingosmotic exchange with sugar solids, while varieties such as Tioga andSenga Sengana are suitable for infusion by this process.

In general, prior to infusion the fruit is de-stemmed, the core isremoved and the fruit is washed and dried. The removal of the stem of afruit is sufficient to create a site for infusion of the sugar solidsfrom the bath into the interstices of the fruit. However, where wholefruits are treated, additional sites may be created by pricking the skinof the fruit, or scarifying the fruit by providing longitudinal orlatitudinal slits on the surface of the whole fruit. Alternatively, thefruit may be sliced, partially or entirely peeled, or sectioned intofruit pieces of the desired size prior to the infusion step. However,the steps taken to prepare the fruit for infusion may differ as afunction of the properties, or ultimate use, of the particular fruitemployed.

For example, when apples are to be infused, the whole fruit may bewashed, peeled and the core removed. The apple is then cut into slicesof the desired size. In order to prevent browning of the peeled appleslices upon exposure to air, the apple slices may be soaked in an edibleaqueous salt or acid solution, e.g., about 0.1 to about 2% or higheraqueous sodium chloride, sodium metabisulfite, ethylenediaminetetraacetic acid or ascorbic acid solution.

When peaches are infused, the whole peach is washed, de-stemmed and thecore is removed. The peach may then be cut into slices or the entirede-cored peach may be infused. Optionally, the peach skin is peeledaway. The skin may be physically pared away with a knife or otherconventional peeling device, or the skin of a peach (or other fruits)may be removed by immersing the fruit in an aqueous, about 3 to about20%, and preferably about 5% caustic solution of sodium or calciumhydroxide. Browning of peeled peaches is prevented by washing the fruit,followed by bathing in about a 1% ascorbic acid solution.

When cherries are employed, they are de-stemmed and the pit is removedprior to infusion. Either sweet or sour cherries may be employed,including cherries of the following types: Morello, Montmorency, OueenAnn, Tartarian or Bing cherries.

Prior to their addition to the infusion bath, strawberries arepreferably de-stemmed, the core is removed and the skin of thestrawberry is scarified by providing a group of surface slits in thebody of the fruit in order to enhance the infusion process. Slicedstrawberries may also be employed in the infusion process.

Fruits which have been previously frozen, as well as fresh fruits, maybe infused. Frozen fruits are thawed under refrigeration, and any excesswater or fruit juices are drained from the fruit prior to immersing thefruit in the infusion bath.

After the preliminary treatment, the fruit is infused with sugar solidsby immersing the fruit in a circulating, solutes-containing bathcomprised of a fructose containing solution.

The amount of infusion bath employed relative to the weight of fruittreated will vary, but in general a weight ratio of fruit to infusionbath of from about 0.1:1 to about 0.75:1, and preferably about 0.5:1,may be employed. During infusion the entire body of the fruit should besubmerged in the bath.

The fruit is immersed in the solutes-containing infusion bath until thetotal water soluble solids content of the fruit is from about 32 toabout 58%, preferably about 35 to about 50%, and most preferably about40-45% water soluble solids. The foregoing percentages are weightpercents, and the percentages given throughout this specification areweight percents unless otherwise specified.

FIG. 1 schematically illustrates one embodiment of an apparatus usefulfor carrying out the process of the present invention.

With reference to FIG. 1, inlet valve 6 is opened, and infusion tank 2is loaded with an aqueous fructose containing, high-Brix syrup which ispumped into infusion tank 2 by pump 5 from high-Brix syrup holding tank4. The prepared fruit 1 is then added to infusion tank 2, with valves 6,7, 11 and 12 in the closed position. Valve 7 is opened, and the syrup iscirculated through the infusion tank via pump 8 and heated by heater 9to a temperature of about 60°-150° F., and preferably to a temperatureof about 80°-125° F. to begin the infusion process. During infusion thefruit pieces 1 are held below the surface of the circulating syrup byscreen 3.

Optionally, the loaded tank may be evacuated prior to beginning thesyrup circulation. A preferred method of evacuation is to reduce thepressure above the syrup to about 20-30" of Mercury, return the pressureto one atmosphere, and to repeat this cycle 2-4 times to insure thoroughdegassing of the infusion mixture.

The initial solids concentration of the circulating syrup is set atabout 30 to about 84% sugar solids, and preferably at about the 65-75%solids level. The circulation rate for 2500-3500 lbs. of syrup ispreferably maintained at about 30-45 lbs./min. during the course of theinfusion process.

The sugar component of the syrup is comprised of at least about 35 toabout 100% fructose, and preferably about 42% to about 90% fructose. Thebalance of the sugar solids may be comprised of dextrose or any of anumber of saccharide materials including monosaccharides, disaccharidesand polysaccharides and their degradation products, e.g., pentosesincluding aldopentoses, ketopentoses like xylose and arabinose, adeoxyaldose like rhamnose, hexoses and reducing saccharides such asaldohexoses like glucose, galactose and mannose; the ketohexuloses, likesorbose and xylulose; disaccharides, like maltulose, lactose andmaltose; nonreducing disaccharides such as a sucrose, otherpolysaccharides such as dextrin and raffinose, and hydrolyzed starcheswhich contain as their constituents oligosaccharides. The balance of thesugar solids may be of a low molecular weight so as to offer asubstantial effect in increasing the osmotic pressure of the sugarsolution. The balance of the sugar solids may also be comprised ofpolyhydric alcohols such as glycerol and the like. When polyhydricalcohols are employed, they preferably comprise only about 1 to about10% of the sugar component.

A commercially available fructose-dextrose corn syrup may be adjusted tothe desired percent sugar solids by water addition, and employed as thesugar-containing infusion bath of the present infusion process. Thesugar solids component of suitable 70-80 Brix fructose-dextrose syrupsmay be comprised of about 50% dextrose, 42% fructose, 1.5% maltose, 1.5%isomaltose, and 5% high saccharides (i.e., Isosweet®, A. E. Staley,Decater, Ill.); or 55% fructose and 42% dextrose, or 90% fructose and10% dextrose.

When the fruit is contacted with the, e.g., 69-71 Brix syrup and theinfusion process begun, the syrup solutes concentration initially drops,for example, to 55-65%, as the syrup is diluted with exfusing andsurface fruit water. However, employing the process of the presentinvention, the syrup solutes concentration is rapidly stabilized,preferably at about 62-67%, during the remainder of the infusionprocess, i.e., until the water-soluble fruit solids have increased fromabout 9-11% to the desired 35-50%.

During the infusion process of the present invention, the concentrationof the infusion bath is stabilized by intermittently, or preferably bycontinuously adding fresh high Brix syrup into infusion tank 2 andwithdrawing diluted syrup from the tank via outlet valve 12. The highBrix syrup is adjusted to the desired sugar concentration by premixing acommercially available syrup such as high fructose corn syrup from tank37 with fixed amounts of pasteurized low Brix syrup from tank 38 viamixing valve 39. The rate of introduction of syrup into the tank, andthe rate of removal of syrup via outlet valve 12 is adjusted so that therate of depletion of sugar solids from the bath due to infusion of sugarsolids into the fruit and concomitant dilution of the bath with fruitwater is at least about equal to, or is slightly less than the rate ofenrichment of the sugar solids resulting from the continuousintroduction of fresh sugar syrup from high Brix syrup holding tank 4via inlet valve 6. During the infusion process, the level of syrup inthe infusion tank 2 remains about constant, and the concentration ofsugar solids in the infusion bath is likewise stabilized at a constantvalue.

The syrup withdrawn from tank 2 is periodically monitored for solutescontent, for example, every 30 minutes at outlet valve 12 by means of aBrix-calibrated refractometer. See Analytical Methods 31.011 and 22.018,AOAC, 13th ed. (1980). In the event that the sugar solutes content ofthe exiting syrup falls below the desired level, it is enriched byincreasing the influx of fresh syrup from holding tank 4, whilesimultaneously increasing the outflow of diluted syrup via outlet valve12. To maintain an infusion bath at about a 65% solutes level employing70-75 Brix syrup inflow into a 600 gallon infusion tank containing about2900 lbs. of syrup and about 1200 lbs. of fruit, an inflow/outflow rateof about 2-9 gal./min. may be employed, preferably the rate will befixed at about 5-7 gal./min.

As will be explained hereinbelow, the outflowing syrup will be treatedby the method of the present invention so as to decrease its viscosityand increase its concentration so that it may be returned to the highBrix holding tank 4 in a condition suitable for reintroduction into theinfusion tank 2. This treatment enables the instant fruit infusionprocess to be carried out while minimizing the use of large amounts offresh syrup, i.e., from tanks 37 and 38, beyond the amounts required forthe initial loading of the infusion tank.

In accord with the practice of the present invention, the 50-60 Brixsyrup stream which exits the infusion tank via outflow valve 12 is firstpassed through a strainer 13 to remove solid matter such as pulp, seeds,and the like.

During the infusion process, pectin lost from the infused fruit greatlyincreases the viscosity of the syrup. The viscosity would be increasedfurther if this syrup were to be subjected to an evaporation step toincrease the sugar solids content. The increased viscosity acts to slowthe infusion process as well as to decrease the flow rate of the syrup.The filtered syrup stream is, therefore, moved via pump 14 into atreatment tank 15 where it is titrated with an amount of a pectolyticenzyme ("pectinase") sufficient to substantially digest the fruit pectinpresent in the syrup and thus to lower the viscosity of the syrup.Useful pectolytic enzymes include Ultrazym® and Pectinex® 3XL (NovoLaboratories, Inc., Wilton, Conn.)

It has been found that the addition of about 1 oz. of commerciallyavailable pectinase per 1000 gal. of syrup is sufficient to lower thesyrup viscosity from about 100 cps (as measured with pectinase at about22° C.) to less than or about 50 cps so that the concentration step canbe efficiently performed.

After enzyme treatment in tank 15, the syrup is admitted via valve 16into a short-time, multiple effect, multistage ("flash") evaporator 17in order to raise the solutes concentration of the syrup to the desired70-74 Brix. The syrup is quickly heated to about 186° F. via boiler 18under a vacuum of about 26-27 inches of mercury. This drives offsufficient water to raise the solutes concentration of the syrup streamto at least 70 Brix, a concentration at which the syrup ismicrobiologically stable if surface-protected. The concentrated syrupexits from the evaporator at about 80° F. and returns to the high Brixholding tank 4 via valve 30, from which it may be pumped back into theinfusion tank, thus completing the reconcentration loop. As notedhereinabove, syrup is continuously passed through this loop at about 2-9gal./min. as soon as treatment tank 15 accumulates a sufficient amountof enzyme-treated syrup.

One flash evaporator which is useful in the practice of the presentinvention is the T.A.S.T.E.® (thermally-activated, short-timeevaporator) manufactured by Gulf Machinery, Safety Harbor, Fla. Thisevaporator is able to produce reconcentrated syrup at the rate of about500 gal./hr. The steam which escapes from the boiling syrup carries withit much of the fruit essence, or essential flavor oils. The T.A.S.T.E.®evaporator also separates the fruit essence from the bulk of thedistillate. The essence is accumulated in holding tank 20 while theexcess waste water is drained off via outlet 19.

The progress of the infusion is followed by periodically removing fruitpieces from the infusion tank, rinsing them and blotting them to freethem of surface syrup and then squeezing out a portion of internal juicewhich is checked for total solutes via a refractometer.

When the fruit has been infused to the desired solutes level, i.e., to35-50% solutes, the circulation pumps are stopped and valves 6, 7 and 12closed. The infusion syrup is then drained from the infusion tank 2 viaoutlet valve 12 and processed as described hereinabove. The infusedfruit is then dumped from the tank via outlet valve 11, and drained andcooled to 20°-30° C. on screen 13. The fruit may then be packed incontainers 25 for shipment. Preferably infused fruit is packed withsyrup of the same Brix in a syrup to fruit w/w ratio of 1:3-6. In thepacking step, for example, 400 lbs. of 40-45 Brix infused fruit ispacked with 100 lbs. of 40-45 Brix syrup which is introduced intocontainer 25 from holding tank 38 along with an appropriate amount offruit essence from holding tank 20 via mixing valve 22.

Alternatively, the infused fruit can be readily dried, i.e., freeze oroven-dried, to about the 15-28% moisture level without undue shrivellingand while maintaining satisfactory organoleptic properties.

The invention will be further described by reference to the followingdetailed examples.

EXAMPLE I Infusion of Apples

Fresh Golden Delicious Apples were washed, peeled, wiped, sliced andsoaked in a 2% solution of sodium metabisulfite solution for one hour. A650 gal. infusion tank was charged with 1225 lbs. of the apple slices(10.5 Brix) which were suspended in 2870 lbs. of 69 Brix high fructosecorn syrup (fructose/total sugar solids=0.42) which was pumped throughthe heated circulation loop at 40 gal./min. and heated to 120° F. A dropin the concentration of the bath from 69 Brix to 60 Brix was observedduring the first 30 minutes of the infusion process at which point freshsyrup was introduced into the tank and diluted syrup withdrawn from thetank at a rate of 5 gal./min. After 30 minutes, the bath concentrationhad stabilized 65-67 Brix. The run was terminated after 110 minutes, atwhich point the syrup Brix was 66.3 and the fruit Brix had been raisedto 46.5, while the total fruit weight had dropped to 726 lbs. Theinfused apple slices were judged excellent in taste and texture andexhibited minimal browning and shrinkage.

EXAMPLE II Fruit Infusion

The results of nine infusion runs employing the general method ofExample I are summarized in Table I. In all cases the bath was heatedand recirculated at 40 gal./min. Syrup was concentrated and returned tothe bath at a rate of 4.0 gal./min. in all runs with the exception ofIIA (5.0.), IIF (2.6) and IIH (2.0). The weight of fruit infused was1200 lbs. (strawberries), 900 lbs. (peaches), 192 lbs. (grapes, I), and385 lbs (grapes, J).

    __________________________________________________________________________             INITIAL             FINAL                                                     SYRUP STABILIZED                                                                            INITIAL                                                                             FRUIT                                                                              RUN                                                  BRIX  SYRUP   FRUIT BRIX TIME FRUIT                                  RUN FRUIT                                                                              (WT.) BRIX    BRIX  (WT.)                                                                              (TEMP.)                                                                            QUALITY*                               __________________________________________________________________________    A   Sliced                                                                             65    65      9.0   40   2.25 hr.                                                                           Excellent                                  Straw-                                                                             (2750               (625 (120° F.)                                berries                                                                            lbs.)               lbs.)                                                (Tioga)                                                                   B   Sliced                                                                             71    63.1    9.5   38.5 1.25 hr.                                                                           Excellent                                  Straw-                                                                             (2872)              (699)                                                                              (110° F.)                                berries                                                                       (Tioga)                                                                   C   Sliced                                                                             71    64.5    9.5   40   1.75 hr.                                                                           Excellent                                  Straw-                                                                             (2872)              (702)                                                                              (114° F.)                                berries                                                                       (Tioga)                                                                   D   Whole                                                                              71    58.5    9.5   40.5 1.25 hr.                                                                           Good                                       Straw-                                                                             (2872)              (740)                                                                              (117° F.)                                berries                                                                   E   Whole                                                                              67    64      9.0   40   6.0 hr.                                                                            Fair                                       Straw-                                                                             (2872)              (650)                                                                              (121° F.)                                berries                                                                   F   Sliced                                                                             69    60.0    10.5  40.0 3.0 hr.                                                                            Excellent                                  Peaches                                                                            (2870)              (542)                                                                              (130° F.)                            G   Sliced                                                                             71.0  64.5    10.1  39.5 2.0 hr.                                                                            Excellent                                  Peaches                                                                            (3420)              (486)                                                                              120° F.)                             H   Sliced                                                                             71    66.3    11    45   3.5 hr.                                                                            Poor                                       Peaches                                                                            (2964)              (514)                                                                              (110° F.)                            I   **Grapes                                                                           69.3  68.5    18.0  41.0 7.5 hr.                                                                            Good                                            (3762)              (109)                                                                              (137° F.)                            J   **Grapes                                                                           50.0  66.8    19.0  37.0 7.5 hr.                                                                            Excellent                                       (3850)              (247)                                                                              (135° F.)                            __________________________________________________________________________     *Taste, Color and Shrinkage.                                                  **Thompson Seedless grapes prepared by destemming and scarification. The      infused grapes were drained, rinsed and freezedried to an 18% moisture        level. "Fruit Quality" is that of the infused fruit before drying.       

It can be seen from the above examples that a variety of fruits can berapidly infused to a high solutes level by the process of the presentinvention. Generally, the quality of the fruit decreased for longerinfusion times, the fruit becoming overly soft and fragile and losingcolor. Grapes, even when pre-punctured, required longer than averageinfusion times due to the density of the membrane. However, grapes werealso more resistant to shrinkage, softening, etc. Infusion times of1.0-3.0 hrs. gave excellent quality fruit in the case of slicedstrawberries, sliced apples, and sliced peaches in that the color andflavor were not adversely effected and little or no shrinkage wasobserved.

While certain representative embodiments of the invention have beendescribed herein for the purposes of illustration, it will be apparentto those skilled in the art that modifications therein may be madewithout departing from the spirit and scope of the invention.

We claim:
 1. A process for infusing fruit with sugar solutescomprising:(a) suspending the fruit in a rapidly circulating heatedaqueous bath initially incorporating about 30-84 percent dissolved sugarsolutes, said sugar solutes being comprised of about 35 to about 100percent fructose; (b) inhibiting dilution of the bath caused by exfusingfruit water by introducing concentrated sugar solution into the bath andwithdrawing substantially equal amounts of diluted syrup so as tostabilize the bath solutes concentration; (c) enzymatically treating thewithdrawn, diluted syrup so as to reduce its pectin viscosity; (d)concentrating the diluted syrup evaporation; (e) returning theconcentrated syrup to the infusion bath; and (f) withdrawing the fruitfrom the bath when the concentration of sugar solutes has been raised tothe desired level before detrimental shrinkage occurs.
 2. The process ofclaim 1 wherein the bath dilution is inhibited by continuouslyintroducing the concentrated sugar solution while simultaneouslywithdrawing equal amounts of diluted syrup.
 3. The process of claim 1wherein the initial concentration of dissolved sugar solutes in the bathis set at about 65-75 percent and the solutes concentration isstabilized at about 62-67 percent.
 4. The process of claim 1 wherein thediluted syrup is concentrated to about 70-75 percent solids.
 5. Theprocess of claim 1 wherein the diluted syrup is treated with an amountof pectinase to effectively lower its viscosity.
 6. The process of claim1 wherein the bath is heated to about 80-125° C. and circulated at about35-45 gal/min and the concentrated syrup is introduced into the bath atabout 2-9 gal/min.
 7. The process of claim 1 wherein the fruit isinfused to a final solutes content of about from 32-58%.
 8. The processof claim 1 wherein the fruit infused is selected from the groupconsisting of strawberries, peaches, grapes, apples, raisins, cherries,bananas, papaya, blueberries, mellons, pineapple, kiwi, soursop,raspberries, mango, plums and loganberries.
 9. The process of claim 1wherein said evaporation is accomplished by means of a flash evaporator.10. The process of claim 9 wherein said evaporation accomplishes theisolation of a substantial portion of the fruit essence which isreturned to the fruit after the infusion process has been completed. 11.The process of claim 7 further comprising isolating the infused fruitand drying the infused fruit to a moisture level of about 15-28%.
 12. Aprocess for infusing fruit with sugar solutes comprising:(a) suspendingthe fruit in a heated aqueous bath which is circulated at about 35-45gal./min., said bath initially incorporating about 65-75 percentdissolved sugar solutes, said sugar solutes being comprised of about 35to about 100 percent fructose; (b) inhibiting the dilution of a bathcaused by exfusing fruit water by introducing a concentrated sugarsolution into the bath and withdrawing substantially equal amounts ofdiluted syrup at a rate of about 2-9 gal/min so as to stabilize the bathsolutes concentration; (c) enzymatically treating the withdrawn dilutedsyrup so as to reduce its pectin viscosity; (d) concentrating thewithdrawn, diluted syrup by evaporation; (e) returning the concentratedsyrup to the infusion bath; and (f) withdrawing the fruit from the bathwhen the concentration of sugar solution has been raised to the desiredlevel before detrimental shrinkage occurs.
 13. The process of claim 12wherein the diluted syrup is treated, in step (c), with pectinase toreduce its viscosity to less than or about 50 cps as measured at about22° C.